Questions on Inclined Manometers - When Using a Meter Scale

[Dom G]

After rereading a number of threads and thinking about the apparent benefits, I've decided to use a 1000 millimeter scale for my inclined manometer. It just seems to simplify the process.

A few questions I have about this are:

1. Can I still use an inch scale for my vertical (pressure) manometer?

2. Can the amount of rise for the Inclined Manometer be in inches or does it need to be metric as well? I'm assuming it can be inches.

3. Are there any other adjustments that will need to be made to any of the calculations to arrive at CFM at a given pressure? Again, I'm assuming not because each of the two key values needed for calculating cfm are determined separately. But since this is my first bench and I'm still learning, its safer to ask the experts than make an incorrect assumption.

Thanks.

Dom

[gofaster]

I use a percent of flow scale. I tried to attach a picture, but the file is too big

[84-1074663779]

I have done exactly that myself.

The vertical test pressure scale is quite independent, so it can be calibrated in inches of water.

Making the sloping manometer length 1,000mm sure simplifies marking off all the various flow divisions, and it is (for me) a convenient length.

The degree of slope can still be in inches which is rather convenient too. For instance the high end of your 1,000mm long scale can be fixed exactly 12" above the low end.

100% orifice flow will then correspond to 12" of water rise along the full length of the manometer tube.

In this example 100% will raise the water 12", the actual sloping tube length can be in any units you choose, say 1,000mm, 30", or 36" perhaps.

For example marking off the 72% flow division at 84.85281% of scale length is dead easy (848.5mm). Locating 25.455 inches or 30.547 inches accurately along an inch scale is going to be a bit more of a challenge.

[larrycavan]

[larrycavan]

Noticed one more thing...might not be important but I'll just toss it out there for you to think about.

Your inclined scale is 39.3" long. Check the width of your backboard to make sure you've got enough room for the vertical and the inclined plus the room to form a nice bend with the tubing for the inclined go up to the reservoir.

Larry

[Dom G]

Thanks for your responses, especially since it was what I wanted to hear. I do plan to use the inch scale for the vertical manometer and for the rise on the inclined manometer.

Larry, you brought up a couple of issues involving the well and cabinet width.

As far as being able to accommodate both manometers and the well within the backboard on the cabinet here's what I did. I moved the vertical manometer to the outside of the left side of the backboard in easy sight in order to free up about 4" of horizonal space on the backboard. Then I add a small extension to the outside of the right side of the backboard to accommodate the 1 meter length of the inclined manometer and to firmly mount the low end of it. And instead of trying to fit the well on the front of the backboard, I mounted it on the back of the backboard right behind the low end of the scale.

Based on suggests and ideas I obtained from other threads, I made the well out of a piece of PVC that is 8" long with a 2" ID in order to obtain maximum surface area and mounted it horizonally on a spring loaded mechanism I designed with a thumb screw allowing for vertical movement to easily zero the fluid level.

However, I do have a question about the well. Obviously the midpoint of the round piece of PVC is going to have the greatest surface area of fluid. What I'm wondering is whether I should put the fittings for the tubing to attach to the center of the end caps of the PVC formed tube, or below the center point of the end caps? Either way, I would fill the well to the halfway point through a fill hole I made in the pipe.

I guess my concern is whether the well could run low on fluid before the 100% mark is reached on the scale. I've mocked everything up dry, but haven't attached the end caps and filled the well with fluid yet so I thought I would ask here. The surface area of my well is quite big so it may not matter, I just haven't done this before.

Your thoughts please.

Thanks.

Dom

[larrycavan]

Dom,

I have to say, I'm impressed at the thought you're putting into this project prior to building it.

I don't think you're going to have any issue with running the reservoir dry. If it were me, I'd put the feed in the center of the reservoir. Either way I think you'll be fine.

I used 1/8th in tubing for the leg and a section of 5/8" ID clear tubing about 16" long for my reservoir. At full scale on the inclined, the change in the reservoir was about an inch. So with the surface area you're going to have, it will be quite minimal.

Please post some pics of the progress if you get the opportunity.


Larry

[larrycavan]

Forgot to mention...The reason I made my inclined reservoir that way was because my Zero was at the top and 100% at the bottom. The fluid would drop rather than rise.

Larry

[larrycavan]

Inclined Scale

[84-1074663779]

Interesting Larry, why did you do that ?

Every manometer scale I have ever seen, up = more, which seems to me to be more intuitive.

[larrycavan]

I wanted it to work like the Dwyer guages.

[Dom G]

Larry, thanks for the kind words.

The true test of how well I've thought things through and constructed the bench will be in the repeatability and accuracy of it.

I'll try to take some pictures of the bench at this stage this weekend and post them.

Dom

[Thomas Vaught]

Quote by Larry:

"Forgot to mention...The reason I made my inclined reservoir that way was because my Zero was at the top and 100% at the bottom. The fluid would drop rather than rise."

Larry, I assume that you are saying the fluid in the inclined leg would drop (like a dwyer unit)
vs the well dropping?

I did some calcs with 86Rocco's spread sheet
(I believe the second version he sent me) and if the angled tube is .200 diameter (on a 40 inch length) the well had to be .740 diameter or so
if the rise was 13.85 inches high. The 13.85 comes from the simulation of the 1.91 sg fluid
using .826 fluid. .826 fluid is a lot cheaper!

The SF 600 bench uses 1.91 sg fluid in a 6 inch
dwyer inclined manometer. This gives a 50% increase in the flow readings vs the normal .826 fluid readings. a 300 cfm orifice with .826 fluid become a 450 cfm range using the 1.91 fluid in the 6 inch manometer.

Tom V.

[larrycavan]

My scale was based on 12"=100%. I used Dwyer's rather expensive 1.0 blue guage oil for several years. When I replaced the tubing some years later, I went with the green wetting agent and distilled water. I didn't need to expand the scale for readability. It was already long. Now, I've put all the aggrivation of water manometers away in a box.

If I had a Superflow 110, I'd adapt and FP1 to it rather than pay Superflow's price for a flowcom unit. I'll wager I could get the proper orfice diameters for the 9 range combinations configured in the FP1 firmware and save a pocket full of money.

PS...I just went to Superflow's site to verify the number of range combos for that bench...PDF files aggrivate me to no end. They don't belong in web sites except as an optional download. Reproducing the brochures in HTML is no job at all.

Larry